A Semiconductor device may be provided on a device area thereof, which may be defined through a LOCOS (local oxidation of silicon) process and/or an STI (swallow trench isolation) process. A transistor formed as part of a semiconductor device may include a gate, a source and a drain.
A transistor of a semiconductor device may be fabricated by first forming a gate insulating layer on a semiconductor substrate having a STI layer. A poly-silicon layer may then be deposited on the gate insulating layer. A STI layer may electrically isolate devices formed on a semiconductor substrate from each other, thereby preventing malfunction of the devices.
A photolithography process may be performed with respect to a gate insulating layer and a poly-silicon layer, thereby forming a gate electrode. The gate electrode may be formed on a prescribed region of the semiconductor substrate where a STI layer is not formed.
High-density dopants may be implanted onto a semiconductor substrate by using an ion implantation device. A gate electrode may be used as a mask. Source and drain junction areas may be formed on active areas of a semiconductor substrate, which are exposed on both sides of a gate electrode.
As semiconductor devices have become more densely integrated, it is possible to form hundreds of millions of transistors on a single wafer. In addition, as semiconductor devices become smaller, a critical dimension (CD) of a gate electrode of a transistor may be reduced, such that a length of a channel formed below the gate electrode may be shortened. As a result, a threshold voltage (Vth) of a transistor may be reduced, which may cause leakage current in a semiconductor device.